Automobile assembly

ABSTRACT

A method for making an automobile assembly having a moulded plastics structural member and a reinforcing member in which a polymerizable adhesive is employed to bond the two members together and an automobile assembly having a bonded structural member and a reinforcing member. The assembly is suitably used as a “front end carrier” or a bumper system in an automobile.

BACKGROUND TO THE INVENTION

[0001] This invention relates to an automobile assembly, in particularto structural assemblies employed at the front end known as a “front endcarrier” or rear end of an automobile and also to assemblies for use asbumper systems. The invention is especially concerned with automobilestructural assemblies having a reinforcing member and a structuralmember which are connected together by means of an adhesive.

[0002] An automobile bumper system typically comprises a “bumper beam”and a “bumper fascia”. Typically the bumper beam is bolted to thechassis of the automobile and the fascia is connected to the bodypanels. An energy absorption unit is typically disposed between thefascia and beam. A bumper beam is typically made of a rigid material,for example steel and aluminium, to provide structural integrity and animpact reaction surface and may act as a reinforcing member in thebumper system. The “bumper fascia” is shaped so as to abut or to beconnectable to the energy absorption unit and also to have aestheticappeal, it being part of the external part of the bumper system. A“bumper fascia” may typically be made of or comprise a moulded plasticsmaterial.

[0003] Energy absorption units (EAU) may be made of metal, for examplesteel and aluminium, or may be made of plastics material. The EAUcompresses or distorts on impact so absorbing the energy of the impact.Conventional plastic bumper EAUs may be assembled for example by heatingstaking points so as to weld the plastics material of the EAU and thefascia together. This process may however leave undesirable visiblemarks on the fascia.

[0004] The fascia may also be attached to the EAU using mechanicalfixing means.

[0005] The EAU may be connected to the bumper beam or may be locatedclose to but spaced from the beam. Typically, the EAU may be connectedto the beam using mechanical fixing means.

[0006] When the fascia and EAU or the EAU and bumper beam are connectedat localised points, large stresses may be encountered at those pointsleading to failure in the event of a collision and less efficientabsorption of energy along the length of the bumper system.

[0007] A “front end carrier” (hereafter FEC) for an automobile is thatpart of the body of the automobile which joins the two sides of thefront of the automobile together and is aligned transversely so as toenclose a front, typically engine, compartment. The FEC is shaped foraesthetic and functional purposes, and typically houses or is otherwiseused to carry one or more of the lighting assemblies, the cooling systemand the latch by which the bonnet is secured when closed.

[0008] FEC's conventionally are made of at least two parts, a structuralmember and a reinforcing member.

[0009] Usually, the structural member, whether in an FEC or a bumpersystem, comprises a plastics material, for example polypropylene, glassfilled polypropylene or polyamides, which lends itself to shaping in thedesired form. The plastics part of the FEC or bumper system isconventionally produced by moulding using known techniques includingcompression moulding and injection moulding.

[0010] In an FEC, the reinforcing member is employed to provide impactresistance, as well as providing structural benefits such as improveddurability and stiffness. The reinforcement is typically made of ametal, for example steel and aluminium, but may be made from othermaterials capable of providing reinforcement. The reinforcing member istypically attached to the structural member by mechanical fixing, forexample using bolts and screws. However mechanical fixing causesconcentrations of stress at the fixing points between the plasticmoulding and the reinforcement, which may cause the FEC to failmechanically during durability testing.

[0011] As an alternative to mechanical fixing in FEC's, the plasticmoulding may be moulded around and interlock with the reinforcement forinstance by way of providing holes in the reinforcements and forming theplastic moulding in situ so as to secure the two parts together. Thisprocess nevertheless is more expensive than assembling the plasticmoulding and reinforcement using mechanical fixing and also providesless process flexibility. Furthermore, the design and effectiveness inuse of the reinforcement may be compromised by having multiple holes andstructurally less effective geometry which are needed to permit in situformation of the plastic moulding.

[0012] Traditional adhesives do not bond effectively to plasticsmaterials of the type used in FECs and which may be used in bumpersystems due to the low surface energy of the plastic materials. As suchit is believed adhesives have not hitherto been employed for fabricatingFECs, bumper systems and the like.

[0013] Adhesives for use in bonding to low surface energy materials arehowever known. For example U.S. Pat. No. 5,795,657 discloses adhesivecompositions which are said to have excellent adhesion to a variety ofsubstrates especially low surface energy polymers. The adhesivedisclosed in this document relates to organoborane polyamine complexesand especially complexes wherein the polyamine is reaction product ofdye primary amine terminated material and material having at least twogroups reactive with primary amine with an excess of primary aminegroups over groups reactive with primary amine. The complexes may beused in systems that initiate the polymerization of acrylic monomer toyield acrylic adhesive compositions. Such compositions are said to beuseful for bonding low surface energy plastic or polymer substrates.U.S. Pat. No. 5,795,657 refers to organoborane amine complexes used inacrylic adhesives and which may be employed in structural andsemi-structural applications including glass/metal bonding and bondingother types of materials together. Reference is made to bonding plasticto a range of types of materials of which one is metal.

PRIOR ART

[0014] U.S. Pat. No. 5,691,065 relates to organoborane amine complexesand to acrylic adhesives that incorporate initiator systems based onsuch complexes. The adhesives are especially useful in bonding lowsurface energy substrates such as polyethylene, polypropylene andpolytetrafluoroethylene. In the Examples in this document Examples 14 to118 provide data concerning adhesion to a polyethylene substrate or apolytetrafluoro-ethylene substrate. Examples 121 to 125 additionallyinclude reference to adhesion of a polypropylene substrate which isbonded to a substrate of the same material.

[0015] These prior art documents do not contemplate the use of adhesivesto bond reinforcing components to plastic mouldings in automobileapplications in which a combination of practical and technical criteriamust be met. In particular, there is no indication in these documentsthat adhesives may be employed in FEC's or bumper systems which, by thenature of their use, are exposed to impact and high stresses andstrains.

[0016] In view of the widespread consumer use of automobiles, matters ofsafety, such as improved crash resistance, durability and stiffness ofthe FEC and robustness, resistance to heat, chemical inertness andrecoverability in low speed impacts of bumper systems, together withcost and manufacturing flexibility are critical in the design andmanufacture of automobiles.

[0017] The known technique of mechanical fixing of the reinforcingmember to the plastic structural member has drawbacks as regardsstructural limitations, and stress concentrations and forming acomponent, for example an FEC and a bumper system by moulding theplastic in situ, for example through holes in the reinforcement, iscostly and inflexible which may limit design options and also increasecosts of production. Producing the components for use in FEC's andbumpers by in situ moulding around the reinforcement also requires themoulding tool to have a complementary design to the reinforcingcomponent so any changes in the design of the reinforcing componentrequire modifications to the moulding tool hence introducing furtherprocess complication and cost. A need remains therefore to improve theoptimum combination of safety, cost and manufacturing flexibility.

SUMMARY OF THE INVENTION

[0018] We have now found a method by which the reinforcing member may beattached to the plastic structural member in automobile assemblies suchas FECs and bumper systems which ameliorates or removes the drawbacksassociated with existing methods of producing them. By employing certaintypes of adhesive which are capable of bonding to low energy surfacessuch as plastics materials used in FECs and bumper systems, the need forattachment through mechanical fixing or in situ formation of a plasticmoulding around a reinforcing component may be reduced or avoided.

[0019] Accordingly, a first aspect of the invention provides a methodfor producing an automobile assembly comprising a structural member madeof a moulded plastics material having a low energy surface and areinforcing member attached to the structural member, the members havingcomplementary surfaces, which comprises applying an adhesive to thecomplementary surface of the structural member and/or reinforcingmember, bringing the complementary surfaces of the reinforcing memberand structural member into contact and allowing the adhesive to set soas to bond the structural member and reinforcing member together whereinthe adhesive is capable of bonding to a low energy surface plastic.

[0020] By low energy surface plastic is meant materials that have asurface energy of less than 45 mJ/m², suitably less than 40 mJ/m² anddesirably less than 35 mJ/m² including, by way of example polypropyleneand polyamide. If desired, the surface of the structural member and/orreinforcing member may be treated or primed to improve adhesion prior toapplication of the adhesive. Suitably the structural member is notsubjected to treatment or priming and the adhesive is applied directlyto the surface of the structural member.

[0021] In a second aspect, the invention provides for the use of anadhesive capable of bonding to a low energy surface substrate in thefabrication of an automobile assembly which comprises a structuralmember comprising a plastic moulding having a low energy surface and areinforcing member to bond together the said moulding and reinforcingmember.

[0022] In a third aspect, the invention provides an automobile assemblycomprising a structural member made of a moulded plastics materialhaving a low energy surface and a reinforcing member attached to thestructural member, the structural member and reinforcing member havingcomplementary surfaces and being attached by means of an adhesive, whichis capable of bonding to a low energy surface substrate, on at leastpart of one or both of the complementary surfaces.

[0023] The present invention may be applied to any automobile assembliesin which a material is to be bonded to a low energy surface material forexample “front end” systems and “rear end” systems and a bumper system.

[0024] Advantageously, the invention permits the structural member andthe reinforcing member to be attached after the structural member hasbeen produced so avoiding the drawbacks of the known process in whichthe structural member is formed in situ. Thus the risk of having toalter the tools for producing the structural member if the reinforcingmember design alters is reduced. Further, the design and hencestructural effectiveness of the reinforcing member is not compromised bylimitations on the geometry, shape or dimensions of the reinforcingmember imposed by the tooling apparatus. The invention accordinglyprovides advantages as regards enhanced process flexibility, design ofthe assembly and cost. In addition reinforcements of a complex designmay be employed to provide a higher level of reinforcement per unitweight of reinforcement. This arrangement may provide additionalbenefits as regards design flexibility, reduced weight with theadvantages that flow from that.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The invention is described with reference to the accompanyingFigures in which:

[0026]FIG. 1 shows a perspective view of a structural member and areinforcing member prior to assembly.

[0027]FIG. 2 shows a perspective view of a part of a bonded automobileassembly.

[0028]FIG. 3 shows a cross-section of the assembly of FIG. 2.

[0029]FIG. 4 shows a cross-section of an alternative design of assemblyto that shown in FIG. 3.

[0030] FIGS. 5 to 8 show cross-section views of different examples ofbumper systems according to the invention.

[0031] FIGS. 9 to 11 show cross-section views of bumper systems in whichthe bumper fascia and the bumper beam are connected through a linkingcomponent.

DETAILED DESCRIPTION OF THE INVENTION

[0032] In a preferred embodiment, the structural member and reinforcingmember have complementary shapes, at least in part and they are bondedtogether by application of adhesive on either or both of thecomplementary parts of the members so as to bond the two parts togetherover an area which is significantly greater than the area associatedwith joining the parts by mechanical fixing. Advantageously, bonding thestructural member and reinforcing member in this manner reduces theconcentration of stress at the joints between the two members.Preferably, the structural member and reinforcing member are bondedtogether by a continuum of adhesive along the complementary surfaces onthe two members in order to reduce the concentration of stress at aparticular point when load is applied to the assembly.

[0033] The automobile assembly, for example a FEC and a bumper system,is suitably manufactured employing known techniques for producing thestructural member for example compression or injection moulding.

[0034] Suitably the structural member comprises a plastic moulding. Theplastics material preferably comprises a homopolymer, for example apolyolefin, a polyamide, a polyphenylene oxide and polystyrene, or acopolymer, for example a polyalkylene terephthalate, having a lowsurface energy.

[0035] Preferred plastics materials include polypropylene, polyamide,polyamide alloys, polyphenylene oxide polymers, polyphenylene oxidealloys, polystyrene polymers, polystyrene alloys, polybutyleneterephthalate polymers and polybutylene terephthalate alloys. Theplastics material may contain fibre, for example short glass fibre, longglass fibre, short natural fibre or long natural fibre.

[0036] Especially preferred plastics materials include short glass fibrefilled polypropylene, long glass fibre filled polypropylene, glassfilled polyamide and glass filled polyamide alloys.—Plastics materialswhich are especially preferred for use in bumper systems as the EAUinclude unfilled polypropylene, talc filled polypropylene, mineralfilled polypropylene]

[0037] The reinforcing member is suitably made of a metal, for examplesteel, zinc and aluminium, but may be made from other materials capableof providing reinforcement. The reinforcing member may be coated withmaterials typically employed in the manufacture of automobiles, forexample anti-corrosion materials and primers for additional coatingssuch as paint.

[0038] In an especially preferred embodiment of the invention in whichthe assembly is a FEC, the structural member is made from glass filledpolypropylene and/or glass filled polyamide and the reinforcing memberis made from steel or aluminium. In a further preferred embodiment, theassembly is a bumper system and the structural member is made frompolypropylene and the reinforcing member is made from steel, aluminiumor polypropylene.

[0039] In a bumper system, the EAU is suitably disposed between thebumper fascia and the bumper beam. The EAU preferably has a generally“C” shaped cross-section. The open ends of the “C” shaped EAU may beconnected to the beam and the opposite side of the “C” connected to thefascia or vice-versa by means of the adhesive. Where the EAU isconnected to the beam by means of the adhesive, the EAU is thestructural member and the beam the reinforcing member. Where the EAU isconnected to the fascia by means of the adhesive, the fascia and EAU arefor present purposes the structural member and reinforcing member.

[0040] The reinforcing member and/or structural member may be providedwith contours or channels which are complementary with the surface ofthe other member so as to provide improved contact and alignment betweenthe structural and reinforcing members. Shaping the members suitablyprovides enhanced resistance to stresses as the adhesion between themembers may be supplemented by physical abutment depending on thedirection in which the stress is applied.

[0041] The adhesive employed in the present invention must be able tobond a low energy surface substrate and also act to bond a secondsubstrate to the low energy surface substrate and, preferably is apolymerizable composition.

[0042] In a preferred method the structural member and reinforcingmember are bonded together by providing an adhesive comprising apolymerizable composition, contacting together the components of theadhesive under conditions for initiating polymerization of the adhesive,applying the adhesive to the complementary surface of the structuraland/or reinforcing member, bringing the complementary surfaces of thereinforcing member and structural member into contact and curing theadhesive so as to bond the said members together. Initiatingpolymerization of the adhesive may be carried out prior to or afterapplication of the adhesive to one or both members or during applicationor as a result of application of the adhesive to one or both members.

[0043] In a preferred embodiment, the adhesive comprises a polymerizablecomposition comprising an organoborane/amine complex and one or more ofmonomers, oligomers or polymers having olefinic unsaturation which iscapable of polymerization by free radical polymerization. Optionally,the adhesive may additionally comprise a compound which causes the saidcomplex to disassociate so as to release the borane to initiatepolymerization of one or more of monomers, oligomers or polymers havingolefinic unsaturation. Where a compound which causes the complex todisassociate is employed, it is kept separate from the complex untilinitiation of polymerization is desired. The polymerizable compositionwhich contains the disassociating agent may be cured at any desiredtemperature, such as at, or near, ambient temperature and below ambienttemperature.

[0044] An especially preferred embodiment of the invention provides anautomobile assembly comprising a structural member made of a mouldedglass filled polypropylene and/or glass filled polyamide having asurface energy of less than 45 mJ/m², and a reinforcing member made fromsteel, zinc and/or aluminium attached to the structural member, thestructural member and reinforcing member having complementary surfacesand being attached by means of an adhesive which is capable of bondingto a substrate having a surface energy of less than 45 mJ/m² disposedbetween at least part of the complementary surfaces so as to bond themtogether, the adhesive being derived from a polymerizable compositioncomprising

[0045] i) an organoborane/amine complex;

[0046] ii) one or more of monomers, oligomers or polymers havingolefinic unsaturation which is capable of polymerization by free radicalpolymerization; and, optionally

[0047] iii) a compound which causes the said complex to disassociate soas to release the borane to initiate polymerization of one or more ofmonomers, oligomers or polymers having olefinic unsaturation.

[0048] Additional especially preferred aspects of the invention are amethod of making the automobile assembly referred to in the precedingparagraph and use of an adhesive described in that paragraph infabricating the assembly described in it.

[0049] Adhesives and polymerizable compositions disclosed inInternational Patent Application No. PCT/US00/33806 are especiallypreferred for use in the present invention to bond the structural memberand reinforcing member together.

[0050] The amines used to complex the organoborane compound can be anyamines which complex the organoborane and which can be decomplexed whenexposed to a decomplexing agent. Preferred amines include the primary orsecondary amines or polyamines containing primary or secondary aminegroups, or ammonia as disclosed in Zharov U.S. Pat. No. 5,539,070 atcolumn 5 lines 41 to 53, incorporated herein by reference, SkoultchiU.S. Pat. No. 5,106,928 at column 2 line 29 to 58 incorporated herein byreference, and Pocius U.S. Pat. No. 5,686,544 column 7, line 29 toColumn 10 line 36 incorporated herein by reference; monthanolamine,secondary dialkyl diamines or polyoxyalkylenepolyamines; and amineterminated reaction products of diamines and compounds having two ormore groups reactive with amines as disclosed in Deviny U.S. Pat. No.5,883,208 at column 7 line 30 to column 8 line 56, incorporated hereinby reference. With respect to the reaction products described in Devinythe preferred diprimary amines include alkyl diprimary amines, aryldiprimary amines, alkyaryl diprimary amines and polyoxyalkylenediamines; and compounds reactive with amines include compounds whichcontain two or more groups of carboxylic acids, carboxylic acid esters,carboxylic acid halides, aldehydes, epoxides, alcohols and acrylategroups. Preferred amines include n-octylamine, 1,6-diaminohexane(1,6-hexane diamine), diethylamine, dibutyl amine, diethylene triamine,dipropylene diamine, 1,3-propylene diamine (1,3-propane diamine),1,2-propylene diamine, 1,2-ethane diamine, 1,5-pentane diamine,1,12-dodecanediamine, 2-methyl-1,5-pentane diamine, 3-methyl-1,5-pentanediamine, triethylene tetraamine, diethylene triamine. Preferredpolyoxyalkylene polyamines include polyethyleneoxide diamine,polypropyleneoxide diamine, triethylene glycol propylene diamine,polytetramethyleneoxide diamine andpolyethyleneoxidecopolypropyleneoxide diamine.

[0051] In particular, the amine in the organoborane/amine complex issuitably selected from the group of amines having an amidine structuralcomponent; aliphatic heterocycles having at least one nitrogen in theheterocyclic ring wherein the heterocyclic compound may also contain oneor more nitrogen atoms, oxygen atoms, sulphur atoms, or double bonds inthe heterocycle; primary amines which in addition have one or morehydrogen bond accepting groups wherein there are at least two carbonatoms, preferably at least three carbon atoms, between the primary amineand the hydrogen bond accepting group, such that due to inter- orintramolecular interactions within the complex the strength of the B—Nbond is increased; and conjugated imines.

[0052] Preferred hydrogen bond accepting groups include the following:primary amines, secondary amines, tertiary amines, ethers, halogens,polyethers or polyamines. Heterocycle as used herein refers to acompound having one or more aliphatic cyclic rings of which one of therings contains nitrogen. The amidines or conjugated imines may bestraight or branched chain or cyclic.

[0053] Desirably, the organoborane used in the complex is a trialkylborane or an alkyl cycloalkyl borane. Preferably this borane correspondsto Formula 1:

B—(R¹)₃   Formula 1

[0054] wherein B represents boron; and R¹ is separately in eachoccurrence a C₁₋₁₀ alkyl, C₃₋₁₀ cycloalkyl, or two or more of R¹ maycombine to form a cycloaliphatic ring.

[0055] Preferably R¹ is C₁₋₄ alkyl, even more preferably C₂₋₄ alkyl andmost preferably C₃₋₄ alkyl. Among preferred organoboranes are tri-ethylborane, tri-isopropyl borane and tri-n-butylborane.

[0056] In a preferred embodiment, the amine part of the complexcomprises a compound having a primary amine and one or more hydrogenbond accepting groups, wherein there are at least two carbon atoms,preferably at least about three, between the primary amine and hydrogenbond accepting groups.

[0057] Preferably, the amine corresponds to Formula 2:

NH₂(CH₂)_(b)(C(R²)₂)_(a)X   (2)

[0058] wherein R² is separately in each occurrence hydrogen or a C₁₋₁₀alkyl or C₃₋₁₀ cycloalkyl; X is hydrogen bond accepting moiety; a is aninteger of 1 to 10; and b is separately in each occurrence an integer of0 to 1, and the sum of a and b is from 2 to 10.

[0059] Preferably R² is hydrogen or methyl.

[0060] Preferably X is separately in each occurrence a hydrogenaccepting moiety and, when the hydrogen accepting moiety is an amine, itis preferably a tertiary or a secondary amine. More preferably X isseparately in each occurrence —N(R⁸)_(e), —OR¹⁰, or a halogen wherein R⁸is separately in each occurrence C₁₋₁₀ alkyl, C₃₋₁₀ cycloalkyl or—(C(R²)₂)_(d)—W; R¹⁰ is separately in each occurrence, C₁₋₁₀ alkyl,C₃₋₁₀ cycloalkyl, or —(C(R²)₂)_(d)—W; and e is 0, 1, or 2. Morepreferably X is—N(R⁸)₂ or —OR¹⁰.

[0061] Preferably, R⁸ and R¹⁰ are C₁₋₄ alkyl or —(C(R¹)₂)_(d)—W, morepreferably C₁₋₄ alkyl and most preferably methyl. W is separately ineach occurrence hydrogen or C₁₋₁₀ alkyl or X and more preferablyhydrogen or C₁₋₄ alkyl.

[0062] Preferably, a is about 1 or greater and more preferably 2 orgreater. Preferably a is about 6 or less, and most preferably about 4 orless. Preferably, b is about 1. Preferably, the sum of a and b is aninteger about 2 or greater and most preferably about 3 or greater.Preferably the sum of a and b are about 6 or less and more preferablyabout 4 or less. Preferably d is separately in each occurrence aninteger of 1 to 4, more preferably 2 to 4, and most preferably 2 to 3.

[0063] Among preferred amines corresponding to Formula 2 aredimethylaminopropyl amine, methoxypropyl amine, dimethylaminoethylamine,dimethylaminobutylamine, methoxybutyl amine, methoxyethyl amine,ethoxypropylamine, propoxypropylamine, amine terminated polyalkyleneethers (such as trimethylolpropane tris(poly(propyleneglycol), amineterminated)ether), aminopropylmorpholine, isophoronediamine, andaminopropylpropanediamine.

[0064] In another embodiment, the amine may be an aliphatic heterocyclehaving at least one nitrogen in the heterocycle. The heterocycliccompound may also contain one or more of nitrogen, oxygen, sulfur ordouble bonds. In addition, the heterocycle may comprise multiple ringswherein at least one of the rings has a nitrogen in the ring. Preferredcompounds of this type include morpholine, piperidine, pyrolidine,piperazine, 1,3,3 trimethyl 6-azabicyclo[3,2,1] octane, thiazolidine,homopiperazine, aziridine, 1,4-diazabicylo[2.2.2]octane (DABCO),1-amino-4-methylpiperazine, and 3-pyrroline.

[0065] In yet another embodiment, the amine which is suitably complexedwith the organoborane is an amidine. Any compound with amidine structurewherein the amidine has sufficient binding energy as describedhereinbefore with the organoborane, may be used. Among preferredamidines are 1,8 diazabicyclo[5,4]undec-7-ene; tetrahydropyrimidine;2-methyl-2-imidazoline; and 1,1,3,3-tetramethylguanidine.

[0066] In a further embodiment, the amine which is complexed with theorganoborane is suitably a conjugated imine. Any compound with aconjugated imine structure, wherein the imine has sufficient bindingenergy with the organoborane as described in International PatentApplication No. PCT/US00/33806 may be used. The conjugated imine can bea straight or branched chain imine or a cylic imine. Among preferredconjugated imines are 4-dimethylaminopyridine;2,3-bis(dimethylamino)cyclopropeneimine; 3-(dimethylamine)acroleinimine;3-(dimethylamino)methacroleinimine.

[0067] Preferably the molar ratio of amine compound to organoboranecompound is from 1.0:1.0 to 3.0:1.0. Below the ratio of about 1.0:1.0there may be problems with polymerization, stability of the complex andadhesion. Greater than about a 3.0:1.0 ratio may be used although theremay not be additional benefit from using a ratio greater than about3.0:1.0. If too much amine is present, this may negatively impact thestability of the adhesive or polymer compositions. Preferably the molarratio of amine compound to organoborane compound is from 2.0:1.0 to1.0:1.0.

[0068] The organoborane amine complex may be readily prepared usingknown techniques, for example as described or referred to inInternational Patent Application No. PCT/US00/33806.

[0069] Preferably, the polymerizable material comprises acrylate and/ormethacrylate based compounds. Especially preferred acrylate andmethacrylate compounds include methylmethacrylate, butylmethacrylate,ethylhexylmethacrylate, isobornylmethacrylate, tetrahydrofurfurylmethacrylate, and cyclohexylmethylmethacrylate.

[0070] The polymerizable composition may further comprise an effectiveamount of a compound that is reactive with an amine so as to liberatethe organoborane so as to initiate polymerization (a disassociatingagent). Desirable amine reactive compounds are those materials that canreadily form reaction products with amines at or below and morepreferably at room temperature so as to provide a composition that canbe generally easily used and cured under ambient conditions. Generalclasses of these compounds include acids, aldehydes, isocyanates, acidchlorides, sulphonyl chlorides, mixtures thereof and the like. Preferredamine reactive compounds are acids, especially Bronsted and Lewis acidsand those described in U.S. Pat. No. 5,718,977 and, more desirablyacrylic acid and methacrylic acid.

[0071] In the polymerizable composition, suitably at least 20% byweight, preferably at least 30% by weight and especially at least 40% byweight of the composition comprises the polymerizable component.Independently, the polymerizable component is suitably present at alevel not exceeding 95%, preferably not exceeding 90% and especially notexceeding 85% by weight of the composition.

[0072] Suitably, the organoborane/amine complex is present at a level ofat least 0.2%, preferably at least 1% and more preferably at least 2% byweight of the composition. Independently, the complex is suitablypresent at a level not exceeding 8%, preferably not exceeding 6% andespecially not exceeding 4% by weight of the composition.

[0073] If present, the disassociating compound is present at a level ofat least 1%, preferably at least 1.5% and more preferably at least 2% byweight of the composition. Independently, the disassociating compound issuitably present at a level not exceeding 8%, preferably not exceeding6% and especially not exceeding 4% by weight of the composition.

[0074] The adhesive to be employed in the present invention suitably iscapable of providing a bond between a 30% glass filled polypropylenestructural member and the reinforcing member without the structuralmember having been subjected to any surface treatment when tested inaccordance with the procedure set out in ASTM D1002. Preferably, theadhesive provides a bond when tested under this regime including inaddition being subjected to thermal cycling and high humidity. Thermalcycling in this context suitably includes cycling over a range from −40°C. to greater than 120° C. Humidity levels can vary from dry to fullysaturated.

[0075] The adhesive may be used in the manner set out in InternationalPatent Application No. PCT/US00/33806. Optionally, further componentsmay be included as additives in the composition. Suitable additivesinclude those set out in International Patent Application No.PCT/US00/33806.

[0076] The assembly suitably is able to withstand exposure to heat at atemperature of 100° C. and suitably at up to 120° C. or more. Further,the assembly desirably should also be able to withstand loads appliedduring production and also imposed in use, for example by slamming thebonnet, application of load to the bonnet latch and vibration andfatigue during use due to displacement from the road surface. The amountand location of adhesive is suitably selected having regard to thedesign and structure of the automobile to which the application applies.

[0077] In fabricating the assembly, the adhesive composition is suitablyapplied to one or both of the members in those areas which are to bejoined. The adhesive is suitably cured at ambient temperature and curingpreferably is initiated prior to the members being brought together. Themembers are then suitably contacted while the adhesive remains able tobond the two members, for example, as the adhesive becomes tacky. Ifdesired, the members may be held in place by mechanical means forexample, snap-fits, mechanical fasteners or temporary clips. Thesurfaces are suitably clean and substantially free of foreign materials,for example fats, oils and water. The complementary surfaces may becomeadhered together relatively quickly so allowing the bonded assembly tobe handled, for example on an automobile production line. The adhesivesuitably continues to cure to provide maximum bond strength and this maytake a period of hours.

[0078] The process conditions employed in bonding the structural memberand reinforcing member together may vary according to the specificadhesive employed.

[0079] By way of illustration only, an adhesive comprising methylmethacrylate as the polymerizable component and an organoborane/aminecomplex as herein described may be applied to a structural membercomprising polypropylene which has not been pretreated, mixed with acuring component and left for a period of 1 to 10 minutes, prior tobringing a steel reinforcing member brought into contact with thestructural member. The adhesive suitably bonds the two memberssufficiently within 10 to 30 minutes after curing is initiated to allowthe assembly to be handled. Subsequently, the adhesive continues to cureto provide a bond of maximum strength after 10 to 30 hours. The processis suitably carried out at ambient temperature.

[0080] As desired, mechanical fixing may be employed in addition toadhesive bonding to hold the structural member and the reinforcingmember together.

[0081] In FIG. 1, a structural member (1) and a reinforcing member (2)are shown prior to bonding together in accordance with the method of theinvention. FIG. 2 shows the members (1) and (2) bonded together afterassembly.

[0082] The structural member (1) is made of a moulded plastics materialhaving a low energy surface and suitably is made of polypropylene orpolyamide and typically is produced by compression moulding or injectionmoulding. The reinforcing member (2) is typically made of steel oraluminium.

[0083] The structural member (1) and the reinforcing member (2) areshaped as desired according to the design of the automobile and areprovided with complementary surfaces (3) and (4) such that the members(1) and (2) fit snugly together and the invention enables the members(1) and (2) to be assembled after being produced.

[0084] Adhesive is applied to part or all of the complementary surface(3) and/or (4) and the reinforcing member (2) and the structural member(1) are brought into contact by relative movement towards each other inthe direction A so that the complementary surfaces (3) and (4) abut oneanother. The adhesive is then cured or allowed to cure to provide abonded assembly according to the invention, a part of which is as shownin FIG. 2.

[0085]FIG. 2 indicates a plane B-B through which a cross-sectionillustration is shown in FIG. 3. In FIG. 3, the reinforcing member (2)has a shallow channel (5) the inside of which defines the complementarysurface (4) into which the complementary surface (3) of the structuralmember (1) is located in manufacturing the assembly. Adhesive is placedon at least part of the complementary surface (3) and/or (4) prior toassembly and forms the bond by which the members (1) and (2) areadhered.

[0086] The structural member (1) is also provided with side channels (6)and (7) and the reinforcing member (2) is provided with lips (8) and (9)which engage with the side channels (6) and (7) in a complementarymanner. The surfaces of the channels (6) and (7) and lips (8) and (9)may be bonded by the provision of adhesive between the respectivesurfaces. Alternatively, these surfaces may not be bonded but in anyevent provide physical abutment between the respective parts of thestructural member (1) and the reinforcing member (2) to enhanceresistance to impact in the direction C, that is from the front of theautomobile and to provide improved alignment between the members (1) and(2) during assembly.

[0087]FIG. 4 shows a cross section of an assembly according to theinvention of a different design to that shown in FIG. 3. The structuralmember (1) and the reinforcing member (2) are aligned and adhered alongcomplementary surfaces (3) and (4). Physical abutment of the members (1)and (2) along lips (10) and (11) and (12) and (13) respectively provideenhanced resistance to impact.

[0088] FIGS. 5 to 8 show a structural member (14) of different design ineach case bonded to a reinforcing member (15) by means of adhesive (16)capable of bonding to a low surface energy plastics material. Thestructural member (14) is made of a plastics materials having a lowenergy surface and suitably is made of polypropylene or polyamide. InFIG. 5, the structural member (14) is a generally “C” shaped EAU and inFIG. 7 the structural member (14) is a blow moulding and in FIG. 8 it isan injection moulding.

[0089] The reinforcing member (15) is typically made of steel or steeland aluminium or may be made of plastics material. In FIG. 6 thereinforcing member (15) is a so-called “close-out” member which meansthat the member (15) is disposed across the open ends of the “C” shapedmember (14) so as to form a box cross section.

[0090] The structural member (14) may have lips (17) as shown in FIGS. 5and 8 and the adhesive (16) may be applied to the lips (17) on or to thereinforcing member (15) at the required location. The adhesive (16) ispreferably applied to either or both the structural member (14) andreinforcing member (15) at all points at which they are in contact.Alternatively, the reinforcing member (15) may have lips (18) to whichadhesive (16) is applied and which are then contacted with thestructural member (14) as illustrated in FIG. 6 or, as shown in FIG. 7,neither the reinforcing member (15) nor the structural member (14) needhave lips.

[0091] FIGS. 9 to 11 show a structural member (14) connected to areinforcing member (15) by means of an adhesive (16) which preferably isemployed along the length of the members (14) and (15). In FIG. 9, thestructural member (14) is an EAU and is made of a polypropylenemoulding. The bumper fascia (19) is spaced apart from member (14) andconnected through conventional means to another part of the vehicle (notshown).

[0092] In FIGS. 10 and 11, the bumper fascia is the structural member(14). The “C” shaped EAU is the reinforcing member (15) and is made ofsteel. The member (15) is spaced apart from the bumper beam (20). Themember (15) is bonded to the bumper fascia (14).

[0093] Suitably, the generally “C” shaped component as illustrated inFIG. 9 (structural member (14)) and FIGS. 10 and 11 (reinforcing member(15)) provides excellent impact resistance properties. Once assembled,the open end of the “C” section is closed by being bonded to the bumperbeam (20) in FIG. 9, the bumper fascia (19) in FIG. 10 and is locatednext to, but not bonded to, the bumper beam (20) in FIG. 11 so creatinga closed box section. The thickness of the box section and the thicknessof the walls defining the box section determine the stiffness of theassembly and the performance of the assembly under impact. Thehorizontal walls, that is the top and bottom part of the “C” shapedcomponent may be designed to buckle under a certain load. This enablesthe impact resistance of the assembly to be tailored according to theintended use. The height of the box section, that is the length of theback part of the “C” shaped component may be tailored to provide desiredproperties according to the intended use.

[0094] Use of an EAU having a “C” shaped cross section is especiallyadvantageous in that the box shaped cross section formed on assemblingthe bumper system possesses excellent strength characteristics whensubjected to impact.

1. A method for producing an automobile assembly comprising a structuralmember made of a moulded plastics material having a low energy surfaceand a reinforcing member attached to the structural member, the membershaving complementary surfaces, which comprises applying an adhesive tothe complementary surface of the structural member and/or reinforcingmember, bringing the complementary surfaces of the reinforcing memberand structural member into contact and allowing the adhesive to set soas to bond the structural member and reinforcing member together whereinthe adhesive is capable of bonding to a low energy surface plastic.
 2. Amethod according to claim 1 in which the low energy surface plasticsmaterial has a surface energy of less than 45 mJ/m^(2.)
 3. A methodaccording to claim 1 in which the plastics material comprises ahomopolymer selected from a polyolefin, a polystyrene and a polyamide ora copolymer.
 4. A method according to claim 1 in which the plasticsmaterial comprises fibre.
 5. A method according to claim 4 in which thefibre is selected from short glass fibre, long glass fibre, shortnatural fibre or long natural fibre.
 6. A method according to claim 1 inwhich the plastics material is selected from short glass fibre filledpolypropylene, long glass fibre filled polypropylene, glass filledpolyamide and glass filled polyamide alloys.
 7. A method according toclaim 1 in which the reinforcement is made of steel and/or aluminium. 8.A method according to claim 1 which comprises applying the adhesivedirectly to the surface of the structural member without treatment orpriming of the said surface.
 9. A method according to claim 1 in whichthe structural member and reinforcing member are bonded together by acontinuum of adhesive along the complementary surfaces on the twomembers.
 10. A method according to claim 1 in which the reinforcingmember comprises contours or channels which are complementary with thesurface of the structural member so as to provide resistance to stressby means of adhesion and/or abutment between the structural andreinforcing member.
 11. A method according to claim 1 in which theadhesive comprises a polymerizable composition.
 12. A method forproducing an automobile assembly comprising a structural member made ofa moulded plastics material having a low energy surface and areinforcing member attached to the structural member, the members havingcomplementary surfaces, which comprises providing an adhesive comprisinga polymerizable composition, contacting together the components of thecomposition under conditions to initiate polymerization, applying theadhesive to the complementary surface of the structural and/orreinforcing member, bringing the complementary surfaces of thereinforcing member and structural member into contact and curing theadhesive whereby the said members bond together.
 13. A method accordingto claim 11 or claim 12 in which the polymerizable composition comprisesan organoborane/amine complex and one or more of monomers, oligomers orpolymers having olefinic unsaturation which is capable of polymerizationby free radical polymerization.
 14. A method according to claim 13 inwhich the polymerizable composition further comprises a compound whichcauses the said complex to disassociate so as to release theorganoborane to initiate polymerization of one or more of monomers,oligomers or polymers having olefinic unsaturation.
 15. A methodaccording to claim 13 in which the amine part of the organoborane/aminecomplex is selected from the group of amines having an amidinestructural component; aliphatic heterocycles having at least onenitrogen in the heterocyclic ring; primary amines which in addition haveone or more hydrogen bond accepting groups wherein there are at leasttwo carbon atoms between the primary amine and the hydrogen bondaccepting group; and conjugated imines.
 16. A method according to claim15 in which the amine is selected from dimethylaminopropyl amine,methoxypropyl amine, dimethylaminoethylamine, dimethylaminobutylamine,methoxybutyl amine, methoxyethyl amine, ethoxypropylamine,propoxypropylamine, amine terminated polyalkylene ethers (such astrimethylolpropane tris(poly(propyleneglycol), amine terminated)ether),aminopropylmorpholine, isophoronediamine, and aminopropylpropanediamine.17. A method according to claim 13 in which the organoborane part of theorganoborane/amine complex is selected from a trialkyl borane and analkyl cycloalkyl borane.
 18. A method according to claim 17 in which theorganoborane is selected from tri-ethyl borane, tri-isopropyl borane andtri-n-butylborane.
 19. A method according to claim 13 in which the molarratio of amine compound to organoborane compound is from 1.0:1.0 to3.0:1.0
 20. An automobile assembly comprising a structural member madeof a moulded plastics material having a low energy surface and areinforcing member attached to the structural member, the structuralmember and reinforcing member having complementary surfaces and beingattached by means of an adhesive, which is capable of bonding to a lowenergy surface substrate, on at least part of one or both of thecomplementary surfaces.
 21. An automobile assembly comprising astructural member made of a moulded glass filled polypropylene and/orglass filled polyamide having a surface energy of less than 45 mJ/m²,and a reinforcing member made from steel, zinc and/or aluminium attachedto the structural member, the structural member and reinforcing memberhaving complementary surfaces and being attached by means of an adhesivewhich is capable of bonding to a substrate having a surface energy ofless than 45 mJ/m² disposed between at least part of the complementarysurfaces so as to bond them together, the adhesive being derived from apolymerizable composition comprising i) an organoborane/amine complex;ii) one or more of monomers, oligomers or polymers having olefinicunsaturation which is capable of polymerization by free radicalpolymerization; and, optionally iii) a compound which causes the saidcomplex to disassociate so as to release the borane to initiatepolymerization of one or more of monomers, oligomers or polymers havingolefinic unsaturation.
 22. An automobile assembly according to any oneof claims 20 and 21 wherein the assembly comprises a front end carrierbeing that part of the body of an automobile which joins two sides ofthe automobile together at the front or rear of the automobile and whichis aligned transversely so as to define a compartment.
 23. An automobileassembly according to any one of claims 20 and 21 wherein the assemblycomprises a bumper system in which: i) the reinforcing member is anenergy absorbing unit made of metal or plastics material and thestructural member is a bumper fascia made of plastics material; or ii)the reinforcing member is a bumper beam made of metal and the structuralmember is an energy absorbing unit made of plastics material..
 24. Anassembly according to claim 23 in which the energy absorbing unit has agenerally “C” shaped cross section.